1、Designation: D3242 11 (Reapproved 2017)Designation: 354/98Standard Test Method forAcidity in Aviation Turbine Fuel1This standard is issued under the fixed designation D3242; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 This test method covers the d
3、etermination of the acidityin aviation turbine fuel in the range from 0.000 mg g to0.100 mg g KOH.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if an
4、y, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized
5、principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D664 Test Method for Acid N
6、umber of Petroleum Productsby Potentiometric TitrationD1193 Specification for Reagent Water3. Terminology3.1 Definitions:3.1.1 acid number, nthe quantity of a specified base,expressed in milligrams of potassium hydroxide per gram ofsample, required to titrate a sample in a specified solvent to aspec
7、ified endpoint using a specified detection system.3.1.1.1 Discussionin this test method, the solvent is atoluene-water-isopropanol mixture and the end point is deter-mined when a green/green brown color is obtained using thespecified p-naphtholbenzein indicator solution.4. Summary of Test Method4.1
8、The sample is dissolved in a mixture of toluene andisopropyl alcohol containing a small amount of water. Theresulting single phase solution is blanketed by a stream ofnitrogen bubbling through it and is titrated with standardalcoholic potassium hydroxide to the end point indicated by thecolor change
9、 (orange in acid and green in base) of the addedp-naphtholbenzein solution.5. Significance and Use5.1 Some acids can be present in aviation turbine fuels dueeither to the acid treatment during the refining process or tonaturally occurring organic acids. Significant acid contamina-tion is not likely
10、to be present because of the many check testsmade during the various stages of refining. However, traceamounts of acid can be present and are undesirable because ofthe consequent tendencies of the fuel to corrode metals that itcontacts or to impair the water separation characteristics of theaviation
11、 turbine fuel.5.2 This test method is designed to measure the levels ofacidity that can be present in aviation turbine fuel and is notsuitable for determining significant acid contamination.6. Apparatus6.1 BuretA 25 mL buret graduated in 0.1 mLsubdivisions, or a 10 mL buret graduated in 0.05 mL subd
12、ivi-sions.NOTE 1An automated buret capable of delivering titrant amounts in0.05 mL or smaller increments can be used, but the stated precision datawere obtained using manual burets only.7. Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise
13、 indicated, it is intended that1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.06 on Analysis of Liquid Fuels and Lubricants.Current edition approved May 1, 2017. Published June 2
14、017. Originallyapproved in 1973. Last previous edition approved in 2011 as D3242 11. DOI:10.1520/D3242-11R17.This test method has been approved by the sponsoring committees and acceptedby the cooperating societies in accordance with established procedures.2For referenced ASTM standards, visit the AS
15、TM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. Unite
16、d StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers
17、to Trade (TBT) Committee.1all reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.3Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to pe
18、rmit its use without lessening theaccuracy of the determination.NOTE 2Commercially available reagents may be used in place oflaboratory preparations when they are certified in accordance with 7.1.7.2 Purity of Water References to water shall be under-stood to mean distilled water as defined by Type
19、III water ofSpecification D1193.7.3 p-Naphtholbenzein4,5Indicator SolutionThep-naphtholbenzein must meet the specifications given in AnnexA1. Prepare a solution of p-naphtholbenzein in titration solventequal to 10 g L 6 0.01 g L.7.4 Nitrogen, dry-type, carbon dioxide-free. (WarningCompressed gas und
20、er high pressure. Gas reduces oxygenavailable for breathing.)7.5 Potassium Hydroxide Solution, Standard Alcoholic(0.01 N)Add 0.6 g of solid KOH (WarningHighly corro-sive to all body tissue both in solid form and in solution.) toapproximately 1 L of anhydrous isopropyl alcohol(WarningFlammable. Vapor
21、 harmful. Keep away from heat,sparks, and open flame.) (containing less than 0.9 % water) ina 2 L Erlenmeyer flask. Boil the mixture gently for 10 min to15 min, stirring to prevent the solids from forming a cake onthe bottom. Add at least 0.2 g of barium hydroxide (Ba(OH)2)(WarningPoisonous if inges
22、ted. Strongly alkaline, causessevere irritation producing dermatitis.) and again boil gentlyfor 5 min to 10 min. Cool to room temperature, allow to standfor several hours, and filter the supernatant liquid through afine sintered-glass or porcelain filtering funnel; avoid unnec-essary exposure to car
23、bon dioxide (CO2) during filtration.Store the solution in a chemically resistant dispensing bottleout of contact with cork, rubber, or saponifiable stopcocklubricant and protected by a guard tube containing soda lime.NOTE 3Because of the relative large coefficient of cubic expansion oforganic liquid
24、s, such as isopropyl alcohol, the standard alcoholic solutionsshould be standardized at temperatures close to those employed in thetitration of samples.7.5.1 Standardization of Potassium Hydroxide SolutionStandardize frequently enough to detect changes of 0.0002N.One way to accomplish this is as fol
25、lows. Weigh, to the nearest0.1 mg, approximately 0.02 g of potassium acid phthalate,which has been dried for at least 1 h at 110 C 6 1 C anddissolve in 40 mL 6 1 mL of water, free of CO2. Titrate withthe potassium hydroxide alcoholic solution to either of thefollowing end points: (1) when the titrat
26、ion is electrometric,titrate to a well-defined inflection point at the voltage thatcorresponds to the voltage of the basic buffer solution; (2)when the titration is colorimetric, add 6 drops of phenolphtha-lein indicator solution and titrate to the appearance of apermanent pink color. Perform the bl
27、ank titration on the waterused to dissolve the potassium acid phthalate. Calculate thenormality using the equation:Normality 5Wp204.2331000V 2 Vb(1)where:Wp= weight of the potassium acid phthalate, g,204.23 = molecular weight of the potassium acid phthalate,V = volume of titrant used to titrate the
28、salt to thespecific end point, mL, andVb= volume of titrant used to titrate the blank, mL.7.5.2 Phenolphthalein Indicator SolutionDissolve 0.1 g6 0.01 g of pure solid phenolphthalein in 50 mL of water, freeof CO2, and 50 mL of ethanol.7.6 Titration SolventAdd 500 mL of toluene (WarningFlammable. Vap
29、or harmful. Keep away from heat, sparks, andopen flame.) and 5 mL of water to 495 mL of anhydrousisopropyl alcohol.8. Procedure8.1 Introduce 100 g 6 5 g of the sample weighed to thenearest 0.5 g, into a 500 mL wide-mouth Erlenmeyer flask.(One type of suitable modified flask is shown in Fig. 1.) Add1
30、00 mL of the titration solvent and 0.1 mL of the indicatorsolution. Introduce nitrogen through a 6 mm to 8 mm outsidediameter glass tube to a point within 5 mm of the flask bottomat a rate of 600 mL min to 800 mL min. Bubble the solutionfor 3 min 6 30 s with occasional mixing.8.1.1 The vapor from th
31、is treatment contains toluene andshould be removed with adequate ventilation.3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for Laborat
32、oryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.4In a 2006 study, only Kodak, Baker (Mallinkrodt), Fluka, and Aldrich werefound to meet the specifications in Annex A1. However, Kodak brand
33、 is no longeravailable.5Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D02-1626. ContactASTM CustomerService at serviceastm.org.FIG. 1 Titration FlaskD3242 11 (2017)28.2 Continue the nitrogen addition and titrate without delayat
34、 a temperature below 30 C. Add 0.01 N KOH solution inincrements and swirl to disperse. When the solution first turnsgreen, reduce the increment size to dropwise (manual buret) orbetween 0.01 mL and 0.05 mL (automated buret). Continueuntil a persistent green end point is reached and held for aminimum
35、 of 15 s after the addition of the last increment.NOTE 4The temperature can be measured by any suitable temperaturemeasuring device.8.3 BlankPerform a blank titration on 100 mL of thetitration solvent and 0.1 mL of the indicator solution, introduc-ing the nitrogen in the same manner and titrating to
36、 the sameend point as above.9. Quality Control Checks9.1 Confirm the performance of the equipment or theprocedure each day it is in use, by analyzing a quality control(QC) sample. It is advisable to analyze additional QC samplesas appropriate, such as at the end of a batch of samples or aftera fixed
37、 number of samples to ensure the quality of the results.Analysis of result(s) from these QC samples can be carried outusing control chart techniques.6When the QC sample resultcauses the laboratory to be in an out-of-control situation, suchas exceeding the laboratorys control limits, instrument recal
38、i-bration may be required. An ample supply of QC samplematerial shall be available for the intended period of use, andshall be homogeneous and stable under the anticipated storageconditions. If possible, the QC sample shall be representativeof samples typically analyzed and the average value andcont
39、rol limits of the QC sample shall be determined prior tomonitoring the measurement process. The QC sample preci-sion shall be checked against the ASTM method precision toensure data quality.NOTE 5Because the acid number can vary while the QC sample is instorage, when an out-of-control situation aris
40、es, the stability of the QCsample can be a source of the error.10. Calculations10.1 Calculate the acid number as follows:Acid number, mg of KOH/g 5 A 2 B!N 356.1#/W (2)where:A = KOH solution required for titration of the sample (8.2),mL,B = KOH solution required for titration of the blank (8.3),mL,N
41、 = normality of the KOH solution, andW = sample used, g.11. Report11.1 Report the result to the nearest 0.001 mg KOH g asAcid Number (Test Method D3242) = (Result).12. Precision and Bias712.1 PrecisionThe precision of this test method as deter-mined by statistical examination of interlaboratory resu
42、lts is asfollows:12.1.1 RepeatabilityThe difference between two testresults, obtained by the same operator with the same apparatusunder constant operating conditions on identical test material,would in the long run, in the normal and correct operation ofthe test method, exceed the following values o
43、nly in one casein twenty (see Table 1).12.1.2 ReproducibilityThe difference between two singleand independent results obtained by different operators work-ing in different laboratories on identical test material would, inthe long run, in the normal and correct operation of the testmethod, exceed the
44、 following values only in one case in twenty(see Table 1).NOTE 6The precision statements were based on the use of manualburets only. The user is cautioned that the precision statements may ormay not be applicable to titrations performed with the use of automatedburets, since no interlaboratory study
45、 has been conducted to date tostatistically evaluate results determined by both techniques.12.2 BiasThe procedure in this test method has no biasbecause the value of the acid can be defined only in terms ofthe test method.13. Keywords13.1 acidity; aviation turbine fuel6MNL 7, Manual on Presentation
46、of Data Control Chart Analysis, Section 3:Control Charts for Individuals, 6th ed., ASTM International, W. Conshohocken,1990.7Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D02-1010. ContactASTM CustomerService at serviceastm.org
47、.TABLE 1 PrecisionANOTE 1All values are in acid number units.Average Acid Number Repeatability Reproducibility0.001 0.0004 0.00130.002 0.0006 0.00180.005 0.0009 0.00290.010 0.0013 0.00410.020 0.0019 0.00570.050 0.0030 0.00910.100 0.0042 0.0128AThese precision data were derived as follows:Repeatabili
48、ty 50.0132aReproducibility 50.0406awhere: a = acid numberD3242 11 (2017)3ANNEXES(Mandatory Information)A1. SPECIFICATIONS FOR p-NAPHTHOLBENZEINA1.1 Conformity RequirementsA1.1.1 AppearanceRed amorphous powder.A1.1.2 ChloridesLess than 0.5 %.A1.1.3 SolubilityTen grams shall dissolve completely in1 L
49、of titration solvent.A1.1.4 Minimum AbsorbanceExactly 0.1000 g of thesample is dissolve in 250 mL of methanol. (WarningFlammable.) Five millilitres of this solution is made up to100 mL with pH 12 buffer. This final dilution should have aminimum absorbance of 1.20 when read at the 650 nm peakusing a Beckman DU or alternative type spectrophotometer,1 cm cells, and water as the blank.A1.1.5 pH Range:A1.1.5.1 Indicator turns to the first clear green at a relativepH of 11 6 0.5 when tested by the method for pHr range ofp-naphtholbenzein
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